1. Field of the Invention
This invention relates generally to an artificial illumination control system for photographic apparatus and, more particularly, to an artificial illumination control system for use with either ordinary flash lamps or other sources of artificial illumination such as a quench strobe.
2. Description of the Prior Art
Electronic photographic strobe devices of the type in which the flashlight produced by the flashtube of the device is automatically terminated after a predetermined quantity of light has been received from the scene being photographed by a light responsive control portion of the device are well known in the art. Such strobes are commonly referred to an quench strobes. In addition to having an independent light responsive control circuit in the strobe, it is also well known to utilize the exposure control circuit associated with the actual camera apparatus to control the firing and quenching of a strobe unit as is more fully disclosed in U.S. Pat. No. 3,776,112 by Wilwerding issued 1973. Wilwerding discloses a circuit coupled to the light integrating exposure control circuit of a camera to effect the flash quenching of an electronic flash unit. Thus, it is well known to couple an electronically controlled shutter camera with a quenchable electronic strobe unit so that the strobe unit is quenched simultaneously with the command signal to return the shutter blade elements to their closed position.
Such an arrangement however would not be compatible with an exposure control system of the type described in a copending application U.S. Pat. (Ser. No. 619,384) entitled "Exposure Control System with Fill-Flash Race Condition" by Edwin K. Shenk, filed Sept. 30, 1975. The aforementioned exposure control system is utilized in conjunction with a shutter blade arrangement of the so-called "Scanning Type" which embodies a pair of shutter blade elements each of which include a primary aperture therethrough to cooperatively define a gradually varying effective aperture size as a function of the position of the shutter blade elements. Each shutter blade element additionally includes a photocell sweep secondary aperture which apertures also cooperatively define a gradually varying effective secondary aperture in front of the exposure control photocell as a function of blade position. The photocell sweep's secondary apertures are generally configured to progessively open ahead of the primary apertures so that the exposure control circuit effects the closing of the shutter blade elements at a time prior to which the film is fully exposed. Prematurely signaling the shutter blade elements to close prior to the time required for a full exposure anticipates for the additional scene light which will impinge upon the film during the finite time required for the shutter blade elements to fully close. Thus, quenching the strobe solely as a function of the exposure control system command signal to initiate closing of the shutter blade elements as disclosed in U.S. Pat. No. 3,776,112, supra, will result in an under-exposure since the strobe is quenched instantaneously. Hence, it has been suggested in a copending application for U.S. patent [our case number 5500] entitled "Artificial Illumination Control System for Photographic Apparatus" by George Whiteside, and Bruce Johnson filed concurrently herewith, that time delay means be utilized in conjunction with a quench strobe.
Hence it is a primary object of this invention to provide a specific embodiment for a time delay circuit which may be utilized in conjunction with a strobe in the manner described in the copending application for U.S. patent [our case number 5500] supra.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the mechanism and system possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.